The present invention relates to an irregular-shaped particle prepared by the method in which a polymer particle is associated with and adhered to other polymer particle, and more particularly to a mono-dispersed irregular-shaped polymer fine particle.
Conventionally, methods of emulsion polymerization, suspension polymerization, and dispersion polymerization are widely known as methods by which particles are prepared by polymerization, and by which spherical particles are easily formed. The irregular-shaped particle is widely used for the basic materials of toners for electrophotography and for paint.
For example, the following method has been disclosed in Japanese Patent Publication Open to Public Inspection No. 266559/1987 in which; after fine particles have been prepared once by the method of suspension polymerization, monomers including a polymerization initiator are added to a dispersing medium so that the monomer reacts with other monomers, and irregular-shaped particles can be obtained. Further, the following method has been disclosed in Japanese Patent Publication Open to Public Inspection No. 51164/1990 in which; fine primary particles having a diameter of not more than 10 .mu.m are made to flocculate together in order to obtain irregular-shaped particles having a diameter of 5 to 25 .mu.m, wherein polyvinyl alcohol, the saponification value of which is 60 to 85%, is used as a dispersing agent.
Further, the following method has been disclosed in Japanese Patent Publication Open to Public Inspection No. 220358/1985, in which; polymer particles are salted out using a salting agent made of acid or its water soluble metallic salts so that aggregated irregular-shaped particles can be prepared.
However, in the aforementioned first example, a large amount of energy is necessary for uniform dispersion, and further, particle sizes are widely distributed, so that it is difficult to prepare irregular-shaped particles with a small diameter. The second example has the same drawback as the first example, and further, has the drawback that it is difficult to separate polyvinyl alcohol, which is used for a dispersing agent, from the particles, so that clean particles can not be obtained.
Further, the third example, which has been disclosed in Japanese Patent Publication Open to Public Inspection No. 220358/1985, has the drawbacks that it is difficult to obtain irregular-shaped particles, the particle size distribution of which is stable, and a large amount of water is necessary to remove a salting agent used for processing.